V. Sizyuk

The effect of excitation wavelength on dynamics of laser-produced tin plasma

We investigated the effect of the excitation wavelength on the density evolution of laser-produced tin plasmas, both experimentally and numerically. For producing plasmas, Sn targets were excited with either 10.6 μm CO2 laser or 1.06 μm Nd:yttrium aluminum garnet laser; both are considered to be potential excitation lasers for extreme ultraviolet lithography laser-produced plasma light sources. The electron density of the plasma during the isothermal expansion regime was estimated using an interferometric technique. The Stark broadening of isolated singly-ionized emission was employed for deducing the density during the plasma adiabatic expansion regime. Our results indicate that the excitation source wavelength determines the initial density of the plasma, as well the plume expansion dynamics. Numerical simulation using HEIGHTS simulation package agrees well with the experimentally measured density profile.

Efficient laser-produced plasma extreme ultraviolet sources using grooved Sn targets

An efficient extreme ultraviolet (EUV) generation method has been developed with the use of a CO2 laser-produced plasma from a grooved target. A ∼5% conversion efficiency from laser to 13.5 nm photons was obtained with the use of grooves in a tin target or by repeated laser pulse shots at the same target position. Modeling studies proved that the groove target controls the hydrodynamic expansion of the plasma leading to confinement which prevents the plasma escaping from the EUV production zone.

Hollow laser self-confined plasma for extreme ultraviolet lithography and other applications

Laser-produced plasma ~LPP! devices are being developed as a light source for the extreme ultraviolet ~EUV! lithography applications. One concern of such devices is to increase the conversion efficiency of laser energy to EUV light. A new idea based on the initiation and confinement of cumulative plasma jet inside a hollow laser beam is developed and simulated. The integrated computer model ~HEIGHTS!was used to simulate the plasma behavior and the EUV radiation output in the LPP devices. The model takes into account plasma heat conduction and magnetohydrodynamic processes in a two-temperature approximation, as well as detailed photon radiation transport in 3D Monte Carlo model. The model employs cylindrical 2D version of a total variation-diminishing scheme ~for the plasma hydrodynamics! and an implicit scheme with the sparse matrix linear solver ~to describe heat conduction!. Numerical simulations showed that the EUV efficiency of the proposed hollow-beam LPP device to be higher than the current standard devices.

Three-dimensional simulation of laser-produced plasma for extreme ultraviolet lithography applications

Laser-produced plasma (LPP) from a tin target is being considered as the light source for the next generation of extreme ultraviolet (EUV) lithography. An integrated model was developed to simulate the plasma behavior and the EUV radiation output in LPP devices. The model includes plasma heat conduction and hydrodynamic processes in a two-temperature approximation, as well as detailed photon radiation transport using Monte Carlo methods. Multiple laser beams incident on a single target have been simulated in full three-dimensional geometry, using the total variation-diminishing scheme for the plasma hydrodynamics and an implicit scheme for heat conduction processes. Numerical simulations showed that EUV conversion efficiency increases for multiple-beam devices with specific optimum laser locations and direction compared to a single-beam device.

Effects of plasma spatial profile on conversion efficiency of laser-produced plasma sources for EUV lithography

Extreme ultraviolet (EUV) lithography devices that use laser-produced plasma (LPP), discharge-produced plasma (DPP), and hybrid devices need to be optimized to achieve sufficient brightness with minimum debris generation to support the throughput requirements of high-volume manufacturing lithography exposure tools with a long lifetime. Source performance, debris mitigation, and reflector system are all critical to efficient EUV collection and component lifetime. Enhanced integrated models continue to be developed using the High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS) computer package to simulate EUV photon emission, debris generation, and transport in both single and multiple laser beam interaction systems with various targets. A new Center for Materials under Extreme Environments (CMUXE) was recently established to benchmark HEIGHTS models for various EUV-related issues. The models being developed and enhanced were used to study the effect of plasma hydrodynamics evolution on the EUV radiation emission for planar and spherical geometry of a tin target and explain the higher conversion efficiency of a planar target in comparison to a spherical target. HEIGHTS can study multiple laser beams, various target geometries, and pre-pulses to optimize EUV photon production. Recent CMUXE and other experimental results are in good agreement with HEIGHTS simulation.

Self-consistent analysis of the effect of runaway electrons on plasma facing components in ITER

Physical and computational models are developed, used and benchmarked for studying the response of ITER tokamak plasma facing components to runaway electron impact following a plasma disruption. The energy deposition, temperature evolution and material melting thickness are calculated for a wide range of runaway electron parameters, namely, electron kinetic energy, magnetic field, energy partition ratio (along and across magnetic field direction) impact duration, and wall material composition. It is shown that the electron energy partition ratio will have a significant effect on the wall heat load with melting of the first wall with beryllium armor possible. If tungsten armor is used instead, the surface of the mockup is overheated and melted for all ranges of studied parameters of the runaway electrons. Using an insert of a thin layer of a high-Z material inside the beryllium armor can mitigate the heat load in the armor and heat sink structure.

Numerical Simulation of Laser-Produced Plasma Devices for EUV Lithography Using the Heights Integrated Model

ABSTRACT Laser-produced plasma (LPP) devices have been modeled as the light source for extreme ultraviolet (EUV) lithography. A key challenge for LPP is achieving sufficient brightness to support the throughput requirements of high-volume manufacturing. An integrated model (HEIGHTS) was applied to simulate the environment of EUV sources and optimize their output. The model includes plasma evolution and magnetohydrodynamic processes in a two-temperature approximation, as well as photon radiation transport determined by the Monte Carlo method. It uses the total variation diminishing scheme for the description of magnetic compression and diffusion in a cylindrical 2-D geometry for the target. Generation of the internal magnetic field with nonparallel density and temperature gradients was also considered. Preliminary results from numerical simulation in hydrodynamics and line radiation output of xenon and tin plasmas are presented for planar and droplet targets.

Damage to nearby divertor components of ITER-like devices during giant ELMs and disruptions

During normal operation of the high confinement mode in future ITER devices, edge-localized modes (ELMs) are a potential threat to the divertor components lifetime and plasma contamination. To predict the outcome of the direct ELM plasma impact on the divertor plate, conversion of plasma energy into radiation in the shielding layer, and then the resulting energy deposition of radiation flux to the surrounding areas, comprehensive physical and numerical models are developed and implemented in the HEIGHTS package. The energy deposition, divertor material erosion, resulting vapour plasma temperature and density evolution, and subsequently the resulting radiation, its transport and deposition around the divertor area are calculated for the predicted ELM and disruption parameters and for the prospective full ITER geometry. The initial simulation results showed that the disrupted plasma power density at the original divertor location and vapour radiation fluxes on nearby dome locations can have the same order of magnitude. The simulation results of the integrated modelling indicate a significant potential damage of the divertor nearby surfaces during giant ELMs and disruption impacts for ITER-like parameters and geometry.

Application of finite-difference methods to membrane-mediated protein interactions and to heat and magnetic field diffusion in plasmas

A robust finite-difference approach for solving physically distinct cross-disciplinary problems such as membrane-mediated protein-protein interactions and heat and magnetic field diffusion in plasmas is described for rectangular grids. Mathematical models representing these physical phenomena are fourth- and second-order partial differential equations with variable coefficients. The finite-difference coupled harmonic oscillators technique was developed to treat arbitrary aggregates of inclusions in membranes automatically accounting for their non-pairwise interactions. The method was applied to study the stabilization of ion channels in a cluster due to membrane-mediated interactions and to examine the effects of anisotropic membrane slope relaxation on the elastic free energy. To obtain contributions from heat and magnetic field diffusion, the splitting method for the physical processes has been used in the numerical solution of resistive magnetohydrodynamic equations. The fully implicit scheme is outlined, tested and applied to problems of the diffusive redistribution of magnetic field and heat in the plasma.

HEIGHTS initial simulation of discharge produced plasma hydrodynamics and radiation transport for extreme ultraviolet lithography

Discharge-produced plasma (DPP) devices have been proposed as a light source for EUV lithography. A key challenge for DPP is achieving sufficient brightness to support the throughput requirements of exposure tools for high-volume manufacturing lithography. To simulate the environment of the EUV source and optimize the output of the source, an integrated model is being developed to describe the hydrodynamic and optical processes that occur in DPP devices. The model includes both plasma evolution and magnetohydrodynamic processes as well as detailed photon radiation transport. The total variation diminishing scheme in the Lax-Friedrich formulation for the description of magnetic compression and diffusion in a cylindrical geometry is used. Several models are being developed for opacity calculations: a collisional radiation equilibrium model, a self-consistent field model with Auger processes, and a nonstationary kinetic model. Radiation transport for both continuum and lines with detailed spectral profiles are taken into account. The developed models are integrated into the HEIGHTS-EUV computer simulation package. Preliminary results of a numerical simulation of xenon gas hydrodynamics and EUV radiation output are presented for various plasma conditions.